What happened
On the morning of 6 February 2024, a Grumman G-164A aircraft, registration ZS-IRW, was engaged in agricultural spraying operations in the Mpumalanga province. After successfully completing eleven chemical loads at Klippan Farm, the pilot departed the private airstrip to return to Middelburg Aerodrome (FAMB).
While climbing through approximately 800 feet above ground level, the engine suddenly stopped. The pilot, noticing the engine was windmilling and observing low manifold pressure with no oil pressure indication, attempted several emergency restart procedures, including adjusting the throttle, mixture, and propeller pitch. Despite these efforts, the engine failed to restart.
Faced with rising terrain and a lack of suitable landing options due to nearby mining pits and a dam, the pilot identified a field to the left. During the forced landing, a combination of a downhill slope and a light tailwind caused the aircraft to float, leading to a touchdown near a berm and ditch. The aircraft sustained substantial damage, including the separation of the engine and the right main landing gear from the fuselage, though the pilot escaped without injury.
The investigation
SACAA AIID investigators examined the wreckage and the aircraft's maintenance history. The investigation confirmed that the pilot was well-rested and held valid commercial credentials. The engine itself showed no signs of pre-existing mechanical failure, and the fuel supply was found to be uncontaminated and free of blockages.
Technical scrutiny focused on the magneto system. While the magneto selector switch appeared functional during basic electrical tests, a detailed internal inspection revealed significant degradation. The investigation established that the magnetos had not been internally inspected or overhauled for 9,695.8 hours since they were installed.
Findings
- The primary cause of the accident was an in-flight engine stoppage, likely triggered by the failure of the magneto selector switch.
- Internal inspection of the switch revealed electrical arcing, foreign material build up, and excessive wear on the contact poles.
- The failure of both magnetos contributed to the loss of engine power.
- The aircraft's landing was complicated by the terrain and the aircraft's tendency to float during the approach.